1. Field of the Invention
The following description relates to a culture apparatus, particularly to a circulatory photobioreactor.
2. Description of the Related Art
Currently, crops cultivated world-wide are used as major food sources for humans. However, yield per acre is not too high and the energy efficiency of solar power is extremely low. On the contrary, photosynthetic microalgae capable of growing underwater with solar energy, carbon dioxide and the use of inorganic salts are favorable since they can be cultivated in areas in which crops do not grow. This provides at least 20 times proteins per acre more than conventional crops and can provide various useful substances and rare natural substances which are not produced in microorganisms, animals and plants. In particular, since algae whose cell size is large precipitate well, isolating them and extracting some substances therefrom is easy. In addition, they use solar energy as a major energy source; thus it is possible to use solar energy efficiently. Further, since they use carbon dioxide as carbon sources and have a photosynthetic system producing oxygen as byproducts, they can alleviate air pollution.
Accordingly, photosynthetic microalgae including genus Chlorella, genus Dunaliella and genus Spirulina, particularly microalgae belonging genus Spirulina (hereinafter referred to as “Spirulina”), is studied vigorously since it is bigger than other photosynthetic microalgae, grows easily in alkali-contaminated environment and can be applied in food, pharmaceutical and other industries. In the meanwhile, temperate regions such as Korea having climate characteristics such as the occurrence of four seasons, dramatic variations of seasonal temperature and sunshine are developing indoor culture technology rather than outdoor culture technology.
For example, Korean Patent No. 235182 discloses a continuing culture apparatus comprising automatic control heater, a culture vessel having an aeration apparatus, a frame having equipments for supporting the culture vessel, a medium-supplying pipe coupled to the side of the frame, a rubber tube for circulating culture solution and a water pump for circulating the culture solution. Korean Patent Gazette No. 2004-0019298 discloses an apparatus for cultivating microalgae comprising a culture vessel molded as a double cylinder-type device consisting of an inner cylinder deposited horizontally and an outer cylinder, wherein at least the outer cylinder comprises a transparent material transmitting light and a gas inlet is opened at the bottom of the culture vessel. Korean Patent No. 679989 discloses a watercourse-type outdoor culture vessel for microalgae in which an inoculation culture vessel for cultivating inoculates is installed and integrated. However, if one cultivates Spirulina using those apparatuses, the grown Spirulina attaches to the surface of the culture vessel excessively. Accordingly, the culture efficiency decreases and one cannot obtain favorable cultural products due to contamination by various germs.
In order to solve the above problems, a method comprising sealing a culture vessel and preventing contamination by various germs by filtering air supplied using a filter was developed. For example, Korean Patent Gazette No. 2002-0057882 discloses an outdoor large scale culture apparatus comprising a device for filtering and UV sterilizing, an air pump, a filtering device, a guide pipe, a filter, a needle valve and a culture vessel and Korean Gazette Patent No. 2002-0083558 discloses a high-density culturing apparatus comprising a culture vessel having a cover on the top side and a pH sensor and dispenser in the culture vessel, a frame for the culture vessel having fluorescent lights, a pH controller, an air pump and a CO2 culture tank.